As integrated circuitry becomes smaller and more dense, needs arise relative to the packaging and interconnecting of fabricated integrated circuitry devices. Concerns associated with increasing the speed with which integrated circuitry devices are packaged and the efficiency with which the devices are packaged drive the industry to find faster and more flexible systems and methods for packaging integrated circuitry. Specifically, one aspect of integrated circuitry packaging includes bonding conductive balls or solder balls on bond pads of a substrate for subsequent connection to packaging structure. Such is commonly referred to as solder ball bumping.
In the formation of solder-bumped substrates, solder ball material is provided over bond pads of a substrate supporting integrated circuitry thereon. If the substrates are to be flip-chip bonded to another substrate, it is important that the solder balls be of uniform size. Otherwise, some of the balls might not make desirable contact with the bond pads of the substrate to which it is to be bonded. This problem led to development of pre-formed solder balls which are formed to a specific common tolerance dimension such that all of the solder balls are essentially the same size. Hence, when the solder balls are bonded by solder melting/welding to substrates, each will essentially project from the outer substrate surface a common distance and accordingly make contact with all bond pads when being bonded.
This invention arose out of concerns associated with providing improved methods and apparatus for packaging integrated circuitry.